Why the He 177 Greif was so Unreliable

The He 177 Greif was big, fast and carried a large bomb load, but it was also terribly unreliable and had a slightly concerning tendency of catching fire in flight. This is well known, with plenty of memes and jokes even dating back to the Second World War, but why did this actually happen? Why was this otherwise promising aircraft doomed from the start?

Well, it was all to do with its overstressed, poorly engineered engines that got so hot they would essentially spontaneously combust. Lets take a look at the He 177 and why it was known as the “Reich’s lighter”.



Germany’s interest in developing the He 177 Greif stemmed from a strategic need to enhance its long-range bombing capabilities, particularly as it prepared for and engaged in the Second World War. The Luftwaffe, under the command of Hermann Göring, recognized the potential value of a powerful strategic bomber that could support Germany’s military objectives by striking deep into enemy territory, disrupting supply lines, and targeting distant cities and industrial centers.

This was seen as vital for Germany’s strategy of quick, decisive victories, especially given the vast geographical areas of the Soviet Union and the need to threaten the UK beyond the range of its existing bomber fleet.

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The Heinkel He 177 Greif (“Griffin”) was a result of this line of thought. Designed in the late 1930s by the German company Heinkel, the He 177 was the only operational long-range bomber capable of carrying a large bomb load at the time for the Luftwaffe.

He 177 captured.
This He 177 was captured and evaluated by the British.

Despite its unique capabilities and the ambitious goals set by its designers, the aircraft was plagued by technical problems throughout its operational life.

The development of the He 177 began under the requirements set by the Luftwaffe in 1936 for a Bomber A, which called for a long-range bomber with the ability to carry a bomb load of at least 1,000 kg over a range of 5,000 km at a speed of 500 km/h (311 mph).

Despite the demanding requirements, the aircraft was only allowed to have two engines. This not only meant they would have to be very powerful, it also reduced redundancy in the event of an engine failure. Heinkel took a very interesting approach to this – instead of using two engines, they used four inside two nacelles.

He 177 front.
The He 177 had the power of four engines, with the frontal area of just two.

This configuration was intended to reduce drag and improve fuel efficiency but led to numerous mechanical and reliability issues, including a propensity for the engines to catch fire. The aircraft’s engines are almost entirely responsible for its infamous reputation for terrible reliability.

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The He 177 was a fast aircraft for its size, and could carry a respectable bombload. It also had a number of forward-thinking features. However, the aircraft was never able to fulfil its potential due to its limited reliability and small production numbers.

He 177 Greif Design

Heinkel’s aircraft featured a number of innovative aspects, most notably its powerplant configuration. As mentioned, the aircraft was powered by four engines, but uniquely, these were paired in two nacelles with the engines coupled together to drive single propellers, known as the DB 606.

The He 177’s airframe was robust, featuring a large, high-wing design with a slight gull wing near the root and fully retractable landing gear. The bomber was capable of carrying a maximum bomb load of up to 7,000 kg in a large internal bomb bay.

He 177 Greif tail gun position.
The He 177’s defensive armament varied throughout its career.

This capacity was actually similar to Allied heavy bombers and enabled it to fulfill its role as a strategic bomber, capable of delivering heavy ordnance deep into enemy territory.

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It was armed with several defensive machine guns and cannon turrets for protection against enemy fighters. These were originally meant to be remote-controlled (as found on aircraft like the B-29), but delays meant the turrets had to be manned. Guns could be found in a dorsal turret, tail turret, and in the nose.

All in, the aircraft was operated by a crew of 6. One of the most advanced features of the He 177 was its pressurized cockpit, a rare attribute for bombers at the time, designed to enhance crew comfort during high-altitude operations.

He 177 Greif bomb load.
The He 177’s bomb load was actually comparable to the Lancaster.

Operational use of the He 177 Greif began in 1942, but its deployment was hampered by ongoing technical problems and the Luftwaffe’s shifting strategic priorities. The bomber was involved in various missions, including long-range bombing campaigns against targets in the Soviet Union and the United Kingdom.

One notable role was its use in the anti-shipping role, where it was equipped with guided missiles and torpedoes. The He 177 was also part of the Luftwaffe’s ambitious, but ultimately unsuccessful, program to develop remote-controlled glide bombs.

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Despite its innovative design and potential, the He 177 did not meet the high expectations set for it. Its service was marred by reliability problems, particularly the engine issues, which were never fully resolved.

A Closer Look at its Engines

The Heinkel He 177 Greif’s engine configuration was one of the most distinctive and problematic aspects of its design. The aircraft carried four engines, but in a highly unusual arrangement intended to reduce drag and improve aerodynamic efficiency, these were paired into two units.

Each unit, known as a Daimler-Benz DB 606, consisted of two Daimler-Benz DB 601 V-12 engines mounted side-by-side and coupled at the crankshaft to drive a single propeller. This complex setup was intended to combine the power of two engines while maintaining the frontal area of just one, thus reducing aerodynamic drag.

The DB 601 alone was already a large, powerful engine. This water-cooled, supercharged, fuel-injected petrol V12 displaced 34 litres (2,070 cu in) and produced 1,100 to 1,400 hp depending on the variant. This engine was one of the main powerplants for the Bf 109, but it also saw use in the Bf 110 and Arado Ar 240.

DB 601 inverted V12.
A DB 601, the same basic type of engine used in many Bf 109s.

As was often with German engines, the DB 601 was inverted (upside down), so the cylinder heads were at the bottom of the engine. This improved the pilot’s visibility over the nose, made access easier during maintenance, and provided room for nose guns above the engine.

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In the 1930s, Heinkel was working on the development of a high-speed, aerodynamically efficient light bomber called the He 119. This aircraft had its cockpit directly behind the nose and completely flush with the fuselage. Two engines were needed to provide the necessary power for this aircraft, but Heinkel didn’t want to mount them in the wings as this induced drag.

Instead, they wanted to combine two engines into one unit which could then fit inside the fuselage and add no additional drag. Daimler-Benz “solved” this by combining two of their DB 601 V12s together to share a common crank. This engine was called the DB 606.

He 119 prototype.
The DB 606 was first used in the He 119.

Technical Details and Challenges

The DB 606 essentially created a 24-cylinder engine from two 12-cylinder engines. The engines were mounted at 44-degree angles, forming a “W” layout.

The coupling of the two engines involved intricate engineering. The engines were, for the most part, separate. Their crankshafts were independent. They were joined by a common gear at the front, which connected their crankshafts to a single propeller shaft.

DB 606 engine.
The DB 606 W24 engine.

This configuration necessitated precise alignment and synchronization of the engines to function properly and avoid mechanical failures. All in the DB 606 displaced 68 litres (4,140 cu in), was 1.6 meters wide and weighed around 1.5 tons. Early versions produced 2,300 horsepower, but this was progressively pushed to around 2,700.

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However, this power came at a significant cost in terms of complexity and reliability.

Reliability Problems

The DB 606 engines became notorious for their mechanical unreliability and tendency to overheat, often leading to in-flight fires. Their first use in the He 119 was relatively trouble-free, but the next aircraft to use them, the He 177 Greif, was much less fortunate.

The engine’s cooling issues were inherent in its design. The inner cylinder banks were close together and their exhaust exits ran parallel to each other at the center of the engine, creating a tight, difficult-to-ventilate area that would get very hot.

DB 606 underside.
Underside of the engine. Note how close together the inner cylinder banks are.

In addition, the engine suffered from poor oil circulation. Due to the angle of the engines, more oil was thrown at the inner cylinder banks, which could seep past the piston rings and affect the timing of the detonation of the fuel/air mix. Known as engine knock, this problem could reduce efficiency and increase temperatures. Engines had to reduce the compression ration in the inner cylinders to combat this.

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The churning of the oil also introduced air into it, creating bubbles and reducing its ability to properly lubricate components. The DB 606 was already finicky and difficult to adequately cool, but the He 177’s nacelles further exacerbated the problem.

The compact engine nacelles, necessary to maintain aerodynamic efficiency, did not allow sufficient space for effective cooling systems. This was partially the result of an odd requirement for the aircraft to be capable of dive bombing.

He 177 Greif front.
The tight cowling and the engines location far back in the wing made its cooling issues worse.

The tight engine configuration and high temperatures often led to failures in the oil and fuel lines. The temperature in the small space between the engines was so hot, that when oil did leak or seep from the engines it would ignite.

Making matters worse, the engine lacked a firewall, so the fire would quickly spread to the wing and the landing gear compartment. If there were any hydraulic fluid leaks in there this would ignite too. Also, dripping oil from the landing gear would fall straight into the bottom-mounted exhaust exits, posing another fire risk.

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The inadequate cooling, combined with the stresses imposed by the linked engines, led to frequent overheating. The bomber was designed for long-range and high-speed missions, requiring the engines to operate at high power settings for extended periods. These strenuous operating conditions further stressed the engines, increasing the likelihood of overheating, mechanical failures and fires.

DB 606 in museum.
The DB 606’s reliability problems were never properly solved. Image by Triple-green CC BY-SA 2.0

The engine issues were so severe that they significantly impacted the He 177’s operational capability. Pilots often referred to the aircraft as a “flying crematorium” due to the frequent engine fires.

Despite various modifications and improvements attempted throughout its service life, including the introduction of newer engine models like the DB 610 (a similar “coupled” setup but based on the more powerful DB 605 engines), the fundamental issues of the power systems were never fully resolved.

Impact on the He 177 Program

The persistent engine problems had a detrimental effect on the He 177’s development and deployment. Many proposed missions and operational roles for the aircraft were curtailed or canceled due to the unreliability of its engines. The issues also consumed considerable engineering resources and attention as mechanics had to ensure there were no oil leaks, diverting effort from other potentially more effective modifications and variants.

DB 610 W24 engine.
The DB 610, shown here, improved on the 606, but still suffered from similar issues.

Efforts to resolve these issues through various modifications were only partially successful. Changes to the engine mounts, enhancements to the cooling systems, and attempts at improving the reliability of fuel and oil lines did not fully address the underlying design flaws. The persistent overheating and the risk of fire remained critical vulnerabilities throughout the aircraft’s service life.

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When discussing the engine, Hermann Göring said “Nobody had told me anything about this hocus-pocus with welded-together engines.”

Operational Usage

Despite these problems, the aircraft was still employed in several key types of missions throughout its service life.

Strategic Bombing Missions

The primary role envisioned for the He 177 was as a long-range strategic bomber. It was tasked with conducting deep penetration bombing raids into enemy territory. Its initial design was intended to allow it to strike distant targets without the need for fighter escorts, due to its high speed and heavy defensive armament.

Greif bombs.
He 177 being loaded with heavy ordnance.

The He 177 participated in bombing missions over the United Kingdom and the Soviet Union, targeting industrial facilities, cities, and other strategic sites. However, the persistent issues with its range and reliability limited its effectiveness and frequency in this role.

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Anti-Shipping Operations

One of the notable roles of the He 177 Greif was in anti-shipping missions, particularly against Allied shipping in the Atlantic and Arctic Oceans. The aircraft was equipped to carry torpedoes and, later in the war, Henschel Hs 293 guided missiles.

These capabilities were employed to attack convoy ships, which were crucial for the Allied supply lines. The He 177’s ability to operate at long range allowed it to reach remote sea lanes that were otherwise relatively safe from air attack.

He 274.
An enlarged, four-individual-engine version of the He 177 was developed, called the He 274.

Specialized Ordnance Delivery

The He 177 was also used to test and deploy specialized ordnance, such as the Fritz X radio-guided bomb, one of the first precision-guided weapons in military history. It was used effectively in the Mediterranean, notably in the sinking of the Italian battleship Roma after Italy’s armistice with the Allies.

Reconnaissance and Other Roles

In addition to these primary roles, the He 177 was occasionally used for reconnaissance missions due to its long range. It could cover vast areas and return with valuable intelligence on enemy positions and movements. There were also proposals to use the He 177 in other specialized roles, including as a carrier for smaller fighter aircraft or drones, though these ideas were not widely implemented.

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After years of dealing with this troublesome aircraft, Germany halted its production in late 1944.